NAME

SYNOPSIS

DESCRIPTION

fsfreeze
halts any new access to the filesystem and creates a stable image on disk.
fsfreeze
is intended to be used with hardware RAID devices that support the creation
of snapshots.

fsfreeze
is unnecessary for
device-mapper
devices. The device-mapper (and LVM) automatically freezes a filesystem
on the device when a snapshot creation is requested.
For more details see the
dmsetup(8)
man page.

The
mountpoint
argument is the pathname of the directory where the filesystem
is mounted.
The filesystem must be mounted to be frozen (see
mount(8)).

Note that access-time updates are also suspended if the filesystem is mounted with
the traditional atime behavior (mount option strictatime, for more details see
mount(8)).

OPTIONS

-f, --freeze

This option requests the specified a filesystem to be frozen from new
modifications. When this is selected, all ongoing transactions in the
filesystem are allowed to complete, new write system calls are halted, other
calls which modify the filesystem are halted, and all dirty data, metadata, and
log information are written to disk. Any process attempting to write to the
frozen filesystem will block waiting for the filesystem to be unfrozen.

Note that even after freezing, the on-disk filesystem can contain
information on files that are still in the process of unlinking.
These files will not be unlinked until the filesystem is unfrozen
or a clean mount of the snapshot is complete.

-u, --unfreeze

This option is used to un-freeze the filesystem and allow operations to
continue. Any filesystem modifications that were blocked by the freeze are
unblocked and allowed to complete.

-V, --version

Display version information and exit.

-h, --help

Display help text and exit.

FILESYSTEM SUPPORT

This command will work only if filesystem supports has support for freezing.
List of these filesystems include (2016-12-18)
btrfs,
ext2/3/4,
f2fs,
jfs,
nilfs2,
reiserfs,
and
xfs.
Previous list may be incomplete, as more filesystems get support. If in
doubt easiest way to know if a filesystem has support is create a small
loopback mount and test freezing it.